Precise force measurement over 6 decades applying the resonator-internal photoelastic effect

Abstract

Mechanical forces can be measured over a range of 6 decades by applying the photoelastic effect inside the laser cavity. Our experiments with a modular test setup (633nm) demonstrate proportional force-to-frequency conversion from 1·10⁻⁴N up to 80N with the noise equivalent resolution of 3·10⁻⁵N. The frequency response of our test setup was established from dc up to some kilohertz. Measurement range and resolution can be extended to 10⁻⁶N or smaller values by applying improved laser stabilization and miniaturizing cavity length and size of photoelastic material. The upper limit of the scale factor is calculated to be of the order of 25MHz/N.